Question

The 15th term of an AP exceeds the 20th term by 8. Find the common difference.​

Answer 1

Answer:

The answer is $-\dfrac{8}{5}$

Step-by-step explanation:

Concept:

If first term of an A.P. is $a$ and common difference $d$, then nth term is given by

                                    $\boxed{a_n=a+(n-1)d}$

Here given  $a_{15}-a_{20}=8$

            $\Rightarrow [a+(15-1)d]-[a+(20-1)d]=8\\\Rightarrow a+14d-a-19d=8\\\Rightarrow -5d=8\\\Rightarrow d=-\dfrac{8}{5}$